n. A provision that prevents an employee from moving the stock they own in the company to other investments until the employee reaches a certain age, usually 55.
The ethical — maybe criminal — core of the scandal is that Enron trapped its employees into a 'stock-lock', whereby they were not allowed to sell share options bought by way of savings. When the company collapsed, they lost everything. Meanwhile, Enron's executives — blessed by inside information and foresight — made a killing by scrambling to sell shares before the price collapsed.
One key question resolves around what Mark Iwry, the senior Treasury official responsible for national retirement savings policy and regulation from 1995 to 2001, refers to as "stock lock." This occurs when a company makes its contribution in its stock and limits workers' ability to diversify out of it. "The law needs to change to give employees the choice [of diversifying] within a reasonable time," Iwry said.
There are two similar phrases floating around in the economic ether: stock lock-up and stock lock-in. However, as near as my high-finance-challenged brain can figure, these refer to a provision whereby an employee can't sell their stocks within a certain number of days after a company has launched an initial public offering.