25 Pa. Stat. § 2837
There may be in each county a county committee for each political party within such county, the members of which shall be elected at the spring primary, or appointed, as the rules of the respective parties within the county may provide. The county committee of each party may make such rules for the government of the party in the county, not inconsistent with law or with the State rules of the party, as it may deem expedient, and may also revoke, alter or renew in any manner not inconsistent with law or with such State rules, any present or future county rules of such party. No such rules shall be effective until a certified copy thereof has been filed in the office of the county board of elections. The members of all other party committees, and all other party officers whose election is required by the party rules, shall also be elected at the spring primary, in the manner provided by this act.
25 P.S.§ 2837