The Russian State Duma passed a bill today that will greatly expand the powers of the Federal Security Service (FSB) and which civil liberties advocates have decried as a grave threat to freedom of speech.

The vote was split down party lines, with the Kremlin-backed United Russia party voting as a bloc in favor of the bill. All deputies from the three other parties voted against it.

The bill was introduced by the Russian federal government on April 24. It will allow the FSB to issue preemptive warnings to individuals or groups that the agency suspects of acting in a way that could potentially become “extremist.” Such extremist activity, it claims, is on the rise in Russia today.

Specifically, the legislation will now allow the FSB to employ “special preventative measures” in order to “eliminate causes and conditions that are conducive to the realization of threats to security” and to issue “official warning notifications about the inadmissibility of actions that bring about the creation of causes of, and which create the conditions for, committing crime.”

What does that mean? In principle, it means that the FSB can do whatever it decides must be done to prevent situations that, theoretically, could lead to a crime being committed.

What that’s going to look like in practice remains to be seen. Experts warn that the legislation is so vague that the agency could easily use it to severely impede upon normal social activism and the normal operation of the press, leading to greater self-censorship by anyone critical of government policy. This concern stems from the fact that allegations of extremism are routinely used by Russian law enforcement agents to stifle legal forms of dissent by human rights activists, oppositionists, artists, journalists, and others.

Vladimir Lukin, the federal human rights ombudsman reappointed by President Dmitri Medvedev in 2009, said that the law was dangerous and discredits the FSB. But calls by critics to veto the legislation expect to go unheeded by the president, as it was the federal government that introduced the bill in the first place.