Vista, a fading survivor of the War on Poverty, appears destined to generate one last shoot-out between the forces of liberalism and conservatism before being put to its final rest by the Reagan administration.

A spat has broken out over guidelines proposed by James Burnley, the new director of the "domestic Peace Corps," that would ban Vista volunteers from engaging in any type of demonstration at any time.

Burnley, a Reagan appointee, wants to be sure than in the last 18 months of its life, Vista will no longer be known as a government program that helps teach poverty groups how to march on city hall or the welfare department.

But the American Civil Liberties Union has cried foul, not so much at the ban per se, but at the idea that it should be in effect around-the-clock, rather than just during working hours.

"Citizens don't give up their First Amendment rights once they become Vista volunteers," argues Arthur Spitzer of the local American Civil Liberties Union chapter, which has filed suit to block enforcement of the rule. "They have a right to do what they want in their off-hours."

Burnley has responded by citing the original Vista charter of 1964, which notes that volunteers are "required to make a full-time personal commitment to combating poverty." He argues that volunteers are supposed to live among the people they serve, and therefore, the distinction between on-duty and off-duty hours is moot.

That, anyway, is what he argued in a memo he wrote to volunteers in July and in a set of proposed guidelines that were published in the Federal Register last month. Once the ACLU filed its lawsuit, however, he decided to make a "more thorough review" of the round-the-clock aspect of the ban. A final notice of the Vista guidelines published in yesterday's Federal Register said the demonstration ban issue would be taken up later.

Whatever the outcome of the flap over demonstrations, the whole thrust of the new guidelines is designed to assure that Vista volunteers are no longer in the business of confrontation politics. "Organizations with a philosophy or pattern of 'confrontational' attacks on other segments of the community have little chance of eliciting the aid of many of the people who can best assist the poor in improving their lot in life," the guidelines say.

And before too long, Vista won't be in any kind of business at all. The program's budget has been slashed in half this year, down to $15 million, and it is scheduled to disappear in fiscal 1983. Burnley said that even though he has been able to reshape Vista into a more conservative agency, he still doesn't think that the volunteer approach to fighting poverty is cost-effective. "We pay those volunteers $6,000 a year," he said, arguing that the money would be better spent in the form of seed grants to local groups that help the poor.