The federal government's campaign to regulate the press goes steadily forward. So far, the litigation has been aimed at financial reporting and publishing, and the government's lawyers have suggested that they only want to tidy up a few loose details in the rules that protect the securities markets. But if they prevail in the cases now moving through the courts, they will establish principles with implications reaching far beyond securities trading.

The Reagan administration keeps emphasizing its burning commitment to reduce regulation. But which is the real and operative policy -- those promises, or the persistent efforts in one courtroom after another to impose new regulatory authority on various aspects of the press?

The solicitor general, Rex E. Lee, told the Supreme Court a few weeks ago that the government has the authority to license publishers of financial periodicals just as it licenses lawyers and barbers. He was arguing an appeal by a newsletter publisher named Christopher L. Lowe; the Securities and Exchange Commission is trying to enjoin him from putting out his newsletter on grounds that he has been convicted of several crimes.

Doesn't it violate the First Amendment to prohibit anybody, criminal record or not, from publishing? Don't worry, says the SEC -- the licensing rules will apply only to newsletters, because the government considers them investment advisers and has no interest in standard newspapers and magazines. Really? That cheery assurance won't survive the Winans case.

R. Foster Winans is the former Wall Street Journal reporter who wrote a stock gossip column and, the government charges, made money speculating on the column's impact on the stocks he mentioned. If he actually did that, he committed a gross violation of ethics and he betrayed his newspaper. But the government goes much further to say it was also a criminal violation of the securities laws. That is an enormous expansion of any previous concept of securities fraud, and if the courts accept this claim, it will subject wide areas of reporting and editing for the first time to federal regulation. The Reporters' Committee for Freedom of the Press, joined by other press organizations, has filed an amicus brief that illuminates these larger concerns sharply.

The First Amendment wasn't written to benefit the publishing industry. It was written to ensure an unimpeded flow of news and commentary to the citizens of a great democracy. No doubt the government's lawyers will protest that they are only trying to keep the undesirables out of the news business. One of these cases revolves around a convicted felon, the other around a spectacular scandal. But the erosion of civil liberties typically begins with cases involving people who are difficult to defend.