Cable industry lawyers have asked a U.S. District Court here to delay implementation of its decision last week upholding the constitutionality of a law granting broadcasters sweeping must-carry protection.The injunction request, if granted, would prohibit broadcasters from demanding carriage on a cable system until an appeal of the district court’s decision could be heard by the Supreme Court. If the injunction request is denied, it’s expected that cable operators ina number of cities nationwide may begin dropping cable programming in exchange for local TV station carriage as early as June. NCTA confab unveils theme The National Cable Television Assn. has settled on “America’s Highway to Tomorrow” as the theme of its June 6-9 annual convention in San Francisco. The 42nd annual confab will focus on the “revolution in technology which will give (cable) a central role in the American telecommunications infrastructure in the 21st Century,” said Dick Roberts, prez of TeleCable Corp. and chairman of the NCTA convention. This year’s convention marks NCTA’s first return to San Francisco since 1961.