Two senators have asked the Justice Department to be “vigilant” as it continues to monitor Google’s actions regarding the standard patents it acquired through its deal with Motorola Mobility.

The Justice Department recently gave its nod to the $12.5 billion deal. But the agency expressed some concern that Google’s attitude toward patents was “more ambiguous” than rivals Apple and Microsoft. Those companies said they will not seek injunctions over patents deemed to cover essential smartphone technology; Google has said that it reserves the right to seek injunctions against companies that do not agree to its licensing terms.

In a letter to Attorney General Eric Holder, Sens. Patrick Leahy (D-Vt.) and Herb Kohl (D-Wis.) wrote that while they take no position on the merits of the deal itself, they hope that the Justice Department will watch the patent space very closely.

“In our view, if a patent is part of a standard and is encumbered by an agreement to license the patent on reasonable and nondiscriminatory terms, an exclusion order may have anticompetitive effects,” they wrote.

They also urged the Justice Department to “use its statutory role as a source of consultation” for the International Trade Commission to ensure that patent rulings are not “misused for anticompetitive purposes.”

Kohl is the chairman of the Senate subcommittee on antitrust, competition policy and competitive rights; Leahy is chairman of the Senate Judiciary Committee.