It's important to understand the distinction between a traditional music publisher and a publishing administrator. Whereas a publisher might take ownership of your copyright, a publishing administrator will simply administer your rights on your behalf but you retain 100% of your rights and can stop at any time.
The Copyright Act of 1976 serves as the basis for much of today's Copyright Law in the United States. One change it brought was the recognition that in certain cases, artists and songwriters were being taken advantage of. Publishers and Record Labels would contractually buy rights to their copyrighted works early on and when the songs reached commercial success years later, the original creators would not be able to reap any of the rewards. This law introduced Termination Rights which allows the original copyright holders, or their heirs, to reclaim ownership rights after 35 years. This helps protect creators who's sold their rights for lower than they were worth when they were starting out, or whose works achieve serious success years later than expected (think "Running Up That Hill" becoming a chart topping hit 37 years after its release).