In 1828, Austin petitioned the legislature to guarantee that slaveowners, immigrating to Texas, could legally "free" their slaves before immigrating, and contract them into a lifetime term of indentured servitude, thereby avoiding recognizing them as slaves. He lobbied to help his colony elude Vicente Guerrero's 1829 attempt to legally emancipate slaves in the province, and to bypass the government's effort to prohibit slavery when it passed the Law of April 6, 1830. In 1830, Austin wrote that he would oppose Texas joining the United States without guarantees that he should "insist on the perpetual exclusion of slavery from this state ." In 1833, he wrote: