Alley Cat Allies is America’s largest group that advocates for the humane treatment of stray and feral cats. They oppose mandatory spay/neuter laws. From their position statement
MSN Diverts Limited Resources Away from Spay/Neuter Programs
In addition to being ineffective, MSN imposes a financial burden on taxpayers and existing government budgets. MSN attempts to increase the spay/neuter rate by imposing penalties on pet owners. Generally, punishment is the most costly way to accomplish any legislative goal. In the case of MSN, government agencies – and the taxpayers who fund them – may incur the expenses of monitoring owner compliance, issuing citations, collecting fines, or participating in court proceedings for disputed citations. Tax dollars, in other words, would be used largely for administrative activities and not on actual spay/neuter programs.