WASHINGTON — ALTHOUGH President Bush lifted economic sanctions against South Africa two months ago, US companies - restrained by local laws and Pretoria's inability to control violence - are not rushing to reinvest in the still white-ruled nation."We don't know of a single company that has gone back in" since Bush lifted sanctions, said Jennifer Kibbe of Investor Responsibility Research Center Inc. (IRRC). The center is an independent, non-profit group that provides analysis on business and public policy issues for 400 of the nation's top institutional investors. The reluctance of US firms to return to South Africa was documented in a new report on "post-sanctions South Africa" based on interviews with more than 40 US company executives, business consultants, bankers, and government officials. Currently, some 290 US companies have either direct investments or non-equity interests in South Africa. Opponents of South African apartheid have waged a decade-long campaign to get US firms to end their ties to South Africa until it transforms itself into a democracy and its majority black population wins full political rights. That drive peaked in 1987, when 56 companies withdrew from South Africa. In subsequent years, fewer firms have quit the troubled nation, including 29 in 1988, 19 in 1989, 10 in 1990, and one so far this year. According to the interviews in the new report, US companies are unwilling to make new investments in South Africa until they see: * The repeal of US state and local laws that restrict business ties to companies doing business in South Africa. * Assurances that South Africa's leaders can end the spiraling violence in the country and that a relatively stable political and economic system will emerge. Currently, a web of 1,434 state and local laws hobble or restrict business or investment ties to South Africa. And, despite the July 10 action by Bush declaring that the white minority government had met the five conditions laid down by Congress in imposing sanctions, state and local governments are resisting lifting the restrictions. "Even the state of Oregon, whose divestment law terminates if the South African government meets five conditions almost identical to the federal statute, has yet to suspend sanctions against South Africa," the IRRC said. A separate study of local sanctions laws by IRRC found two key reasons for local resistance to ending their laws: * Anti-apartheid coalitions, made up of anti-apartheid activists and civil rights, labor and religious groups, argue that Bush's action was premature and that sanctions should remain until Pretoria releases all political prisoners and the nation embarks on an "irreversible" path to democracy and equal rights. * Most of the state, city, and county anti-apartheid laws have no criteria for termination.