SEC would be a start, if this method is being used it's illegal where they don't have to file for 5% ownership 13D and are hiding their transaction.
WHY IT MATTERS:
Warehousing accomplishes several things. First, it allows a potential acquirer to take advantage of short-term dips in the target's share price (in other words, it buys shares when they're "on sale"). Second, it avoids having to buy big blocks of shares in one fell swoop, which can make the stock price spike and reveal the company's real intentions. Accordingly, warehousing allows a company to fly "under the radar" for a time. However, the SEC does require anyone who exceeds a 5% ownership threshold to file a form 13G or 13D, which means the size of the company's position will eventually become public and trackable by others.
BREAKING DOWN 'Parking' Stock parking is an illegal measure by which a broker arranges to sell shares to another party to reduce their position for disclosure deadlines, with the understanding that the the original broker will purchase the shares back later at a profit to their receiving broker. Brokerages try to park stocks to keep their holdings legal under SEC guidelines during disclosure periods, or to appear as though they have fulfilled all of their obligations by the settlement date for a particular trade.
BREAKING DOWN 'Parking Violation' By having a third party hold significant portions of stock, the acquiring company can prepare for a takeover without exceeding certain ownership reporting levels and alerting the target company.
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