Is IPSEC restrcted on some ISP’s networks?

I recently had someone mention that IPSEC is stopped from flowing over some ISP’s networks. Specifically, someone said that Verizon Networks below business class restricts it. I couldn’t find anything to substantiate that from a cursory Googling. Does anyone have any insight into this? Do foreign countries restrict the flow of IPSec or any other encrypted traffic over their backbone?

Thanks!