The statue atop the Ulysses S. Grant Memorial on the Capitol Hill is silhouetted by the Capitol dome in Washington. (AP Photo/Manuel Balce Ceneta)

Republicans are planning to use the annual spending bills to challenge some of President Obama’s best-loved policies, adding another layer to a budget battle that already promises to be messy as the two parties fight over how much money to spend on domestic programs.

The fiscal 2016 spending bills moving through the House and Senate are filled with attempts to block or defund a slew of Obama administration initiatives, including environmental rules, the effort to renew diplomatic ties with Cuba and a Labor Department proposal to crackdown on the retirement savings industry.

While using so-called policy riders on appropriations bills is a time-honored tradition on Capitol Hill, Republicans have signaled they plan to be extra aggressive this year now that they control both chambers of Congress and Obama’s second term is running out.

When the fight over these policy-riders will come to a head is unclear.  The first order of business is figuring out an end to the stalemate over the top-line spending level for the fiscal 2016 appropriations bills, something that could take until the end of the calendar year. Obama is threatening to veto any bill that conforms to the Republican budget plan approved by Congress earlier this year. Senate Democrats are also threatening to filibuster any appropriations bill until a broader deal is reached allowing for more spending on domestic programs.

As negotiations over the broader funding battle progress, at some point in the coming months the policy-riders will likely lead to a showdown between Republicans and Obama.

What follows is a list of which ones could prove most contentious.

Cuba. The Cold War may be long over, but last week’s announcement that the United States and Cuba will open embassies later this month after more than a half-century of diplomatic isolation fueled anger among many Republicans, who are already upset over the administration’s announcement in December that it planned to renew diplomatic ties with the communist country.

The GOP is seeking to thwart the administration’s Cuba agenda by denying funding for key programs.

For instance, the House State and Foreign Operations spending bill includes language banning funds for a new embassy and its operations.

And denying money for opening an embassy in Cuba isn’t the only way Republicans are targeting Obama’s aspirations in Cuba. Rep. Mario-Diaz Balart (R-Fla.), the son of Cuban immigrants, added language to the Commerce, Justice and Science spending bill that would prevent the United States from providing military assistance to Cuba and to the Transportation, Housing and Urban Development bill that would block U.S. airlines and cruise ships from travelling to the island.

“We must not permit the exploitation of properties stolen by the Castro regime, which is expressly prohibited in U.S. law,” Diaz-Balart said in a statement.

Republicans in the Senate are expected to include similar provisions in their spending bills.

“I will do all in my power to block the use of funds to open an embassy in Cuba,” Appropriations Committee member Sen. Lindsey O. Graham (R-S.C.) wrote in a tweet in December. “Normalizing relations with Cuba is bad idea at a bad time.”

Immigration. House Republicans added language, championed by Rep. Steve King (R-Iowa), to the House Commerce, Justice, Science spending bill that would seek to block the Justice Department from following through on any executive actions to indefinitely defer deportation of some undocumented immigrants. Despite a court order that has delayed implementation of these actions, Republicans are still looking to use the budget process to keep Obama from making good on his immigration policy goals.

The bigger fight over taking on the president’s executive orders on immigration will likely take place when the House and Senate consider funding for the Homeland Security Department, which has direct oversight of immigration policies. These bills could be considered later this month.

How hard to push back against the president’s immigration agenda has already proven tricky for Republicans.

Last year Republicans successfully maneuvered to have fiscal 2015 funding for the the department expire earlier this year on a different schedule than other areas of the government. Conservatives in the House and Senate pushed to use the bill to prevent Obama from implementing his immigration plan.

But in March Democrats successfully forced Senate Majority Leader Mitch McConnell (R-Ky.) to abandon a House-passed provision that stripped funding for the deferred action programs clearing the way for the funding bill to be enacted.

The fiscal 2016 appropriations process now gives conservatives a second shot at protesting the president’s immigration policies through the spending bills.

Environment. The Environmental Protection Agency is not just a prime target for Republicans, it is the primary target for McConnell. The Kentucky Republican kept his seat on the Senate Appropriations Committee when he became Majority Leader and took a position on subcommittee that has jurisdiction over the agency.

McConnell successfully lobbied for the Interior and Environment bill to include language that would prevent the EPA from punishing states that decide not to submit a plan for complying with newly adopted rules limiting power plant emissions.

“If enacted, the measure I secured today will guarantee that governors who heeded my warning will be protected, while also prohibiting funding for the EPA to force states to submit an implementation plan,” McConnell said in June. “I joined the Interior Subcommittee this year specifically to be in a position to oversee the EPA’s budget.”

The bill also contains provisions that would block enforcement of clean air and water regulations, limitations of hydraulic fracturing, or fracking, and limitations of mining natural gas on federal land.

This includes language that would prevent the EPA from enforcing a rule that designates which waterways — such as streams, lakes and rivers — fall under the jurisdiction of the federal government. The Waters of the United States regulation, WOTUS, infuriated farmers, oil companies and other groups that say the anti-pollution rules are too restrictive. The issue has become a pet project for Sen. John Hoeven (R-N.D.), who helped ensure that this year’s appropriations bill would block funding for the program. The House bill includes similar language.

Labor. Republicans are using the Labor, Health and Human Services funding bills to block action on everything from a crackdown on retirement advisers to limiting rules for how workers vote on union membership.

Both the House and Senate bills contain language that would block implementation of a proposed Labor rule that would require brokers to act in the best interest of clients saving for retirement rather than steer them into investments that bring in the most fees or other forms of compensation. Many Republicans and representatives from the securities industry strongly oppose the rule, which was proposed in May, arguing the tougher legal standard will make it more expensive for them to do business and could lead them to drop lower-income clients.

But the rule has the strong backing of liberals, including Sen. Elizabeth Warren (D-Mass.), who argue Wall Street is ripping off investors in dire need of a retirement nest egg.

The House bill also would seek to prevent the NLRB from implementing regulations that make it easier for employees to form a union, such as by allowing electronic voting in union elections.

Net Neutrality. House Republicans also want to kill new rules that would allow the government to treat internet providers like public utilities and prevent them from blocking or slowing down any web traffic, no matter the source or destination.

The House Financial Services and General Government spending bill would seek to block the Federal Communication Commission, which released the controversial rule in February, from implementing this net neutrality regulation until a set of court cases are resolved, which could take years.

The bill would also move to require any new regulations to be made public 21 days before the FCC votes on them and would prevent the agency from setting rates for accessing the internet.