Every commercial float shall have a clearance. Clearances may be obtained at such places along the canal system and at such other points as the corporation may direct. No clearance shall be granted to any commercial float unless the person authorized to issue such clearance has evidence that such float is duly registered in the office of the corporation. Each float shall have a separate clearance and no part of the cargo shall be cleared to a place beyond which the float is cleared. The corporation may, in its discretion, refuse to issue a clearance for a vessel against whose registered owner there is an unpaid penalty involving such vessel for the violation of rules and regulations adopted pursuant to this chapter.