https://thinkprogress.org/why-is-jeff-sessions-blocking-a-child-sex-trafficking-bill-e7ebb1428dba#.g8oevxsoo

Some discussion on why it was blocked:

Sessions is pushing back against claims that he believes child victims deserve to be arrested as prostitutes

a Republican Judiciary aide told ThinkProgress that Sessions was instrumental in helping the bill clear the Senate Judiciary Committee but had to object after the House removed two of his amendments that he said toughened the bill.

One measure required a mandatory minimum sentence “for transporting, receiving or distributing” child pornography. The other expanded subpoena authority to the U.S. Marshals Service over unregistered sex offenders.

Scott also dropped the mandatory minimum measure because minimums are “irrelevant, ineffective” sentences that “tend to have a very negative impact on people of color.”