The U.S. Secret Service imposed new rules Friday aimed at tightening oversight of its employees on international trips in the wake of the Colombia prostitution scandal — banning staff members from bringing foreigners into their hotel rooms, drinking alcohol within 10 hours of duty and visiting “non-reputable establishments.”

Senior management distributed the list of 10 rules in a memo to employees, codifying what traditionally had been a largely unwritten code of conduct in the agency. The changes were deemed necessary after 12 agents and officers were implicated in an incident that involved heavy drinking and payments to prostitutes in advance of President Obama’s visit to Cartagena, Colombia, two weeks ago.

Next week, the Secret Service will hold an ethics training session for more than 100 employees, and several more mandatory courses will be scheduled through the year, agency officials told members of Congress. The agency said it hoped to put all of its 3,500 agents and 1,400 uniformed officers through the training seminars.

In the memo, the agency said employees “are expected to always conduct yourselves in a manner that reflects credit on you, the Secret Service, the Department of Homeland Security, and — most importantly — the United States Government and the citizens that we serve.”

Rep. Peter T. King (R-N.Y.), chairman of the House Homeland Security Committee, which oversees the service, called the new guidelines a good step.

“This sends a signal that, when in doubt, don’t do it,” King said.

The Secret Service is conducting an investigation into the allegations, and it has forced out nine employees, while clearing three others of serious misconduct. But new allegations have surfaced of similar misbehavior on other trips, including a presidential visit to El Salvador last year, and agency officials said they will seek to determine if there is evidence of a larger, cultural problem within the institution.

Some former agents said they were surprised that the service has decided that it must spell out the sort of rules that should be understood by anyone working for the agency.

“We’re taught certain principles from day one and throughout our career — acting professionally and ethically and not in a way that embarrasses the service or the president,” said Andrew O’Connell, who spent eight years at the agency before leaving in 1997 to become a federal prosecutor. He now works in private consulting.

“It’s too bad they have to put it into writing, because I think they are better left as general principles about how we’re supposed to act,” he added. “If you can’t live up to those principles, you shouldn’t become an agent.”

Other new rules include required briefings on standards of conduct before each trip, as well as country-specific briefings from State Department officials once the service employees arrive at the foreign location.

Two of the agency employees dismissed after the Cartagena incident were supervisors at the GS-14 pay grade. Under the new rules, each group of agents and officers sent on a foreign trip will be overseen by managers at the GS-15 pay grade.

Prostitution is legal and regulated in Colombia, but the agency announced Friday that all U.S. laws will cover its personnel on the foreign trips.