If the WSCC is operated by a city, county or other municipality, firearms can be prohibited, with exception to CPL holders.
RCW 9.41.290 State Preemption
The state of Washington hereby fully occupies and preempts the entire field of firearms regulation within the boundaries of the state, including the registration, licensing, possession, purchase, sale, acquisition, transfer, discharge, and transportation of firearms, or any other element relating to firearms or parts thereof, including ammunition and reloader components.
Cities, towns, and counties or other municipalities may enact only those laws and ordinances relating to firearms that are specifically authorized by state law, as in RCW 9.41.300, and are consistent with this chapter. Such local ordinances shall have the same penalty as provided for by state law. Local laws and ordinances that are inconsistent with, more restrictive than, or exceed the requirements of state law shall not be enacted and are preempted and repealed, regardless of the nature of the code, charter, or home rule status of such city, town, county, or municipality.
RCW 9.41.300
(2) Cities, towns, counties, and other municipalities may enact laws and ordinances:
(b)
Restricting the possession of firearms in any stadium or convention center, operated by a city, town, county, or other municipality, except that such restrictions shall not apply to:
(i) Any pistol in the possession of a person licensed under RCW
9.41.070 or exempt from the licensing requirement by RCW
9.41.060; or
If the OP has a valid CPL, then he may carry open or concealed.