In a remarkable vote of no confidence this summer, Congress overwhelmingly passed a bill leveling new sanctions against Moscow, curtailing Donald Trump’s ability to negotiate with Vladimir Putin and delivering a stinging rebuke of the president’s refusal to condemn Russian interference in the 2016 election. Trump reluctantly signed the bill into law in early August, but his administration blew past an October 1 deadline to impose the sanctions—and is offering lawmakers no explanation as to why.

Under the law, the White House was required to “issue regulations or other guidance” on how the United States would target Russia with its latest round of sanctions. That guidance has yet to come, though in the meantime, the Trump administration has issued separate sanctions against North Korea and threatened to impose fresh measures against Iran, the two other countries addressed in the legislation. In an effort to hold the White House accountable, lawmakers have met with Secretary of State Rex Tillerson, written letters to the president, and even issued statements calling Trump’s commitment to the bill in question, all to no avail.

For lawmakers concerned by Trump’s repeated overtures to Putin during and after his campaign, the inaction is setting off fresh alarm bells. “If they don’t cooperate, then further actions need to be taken,” Senator John McCain told the Daily Beast on Monday. Even Trump’s new golfing buddy, Senator Lindsey Graham, has raised concerns about the missed deadline. During an interview on NBC’s Meet the Press, the South Carolina lawmaker lamented, “I think the Trump administration is slow when it comes to Russia. They have a blind spot on Russia I still can’t figure out.” (Trump, who has cast doubt on the intelligence community’s assessment that Russia interfered in the presidential race, has suggested partnering with Russia to form a “cyber-security unit” to guard against election hacking.) Graham, a Russia hawk, continued with a warning to Trump: “Russia is going to get worse, not better. Mr. President, go after Russia because they are coming after us.”

When asked by host Chuck Todd what Capitol Hill’s response will be if the White House doesn’t follow through on implementing the sanctions, Graham replied, “Congress will hold the president accountable.” But as the Daily Beast points out, when it comes to enforcing the law it all but forced the president to sign, Congress is essentially powerless. In the end, its only option may be to threaten Trump’s legislative agenda—a tactic Senator Ben Cardin implied it would readily employ. “There are opportunities that we plan to take advantage of. We have hearings, we have appropriations bills—there are a lot of things we can express ourselves on,” he said. “And we’ll use every opportunity we can.”