Only the USG6510E/6510E-POE/6530E do not support MPLS.
License Requirements
The MPLS is not license-controlled.
Restrictions
If both the MPLS and NAT features are deployed on the FW, MPLS and NAT related information is added to the session table, causing the memory usage to surge and concurrent processing capability to decrease. The FW is not supposed to act as the PE while carrying other security services. In this scenario, deploying a Layer 3 switch as the PE is recommended.