Is it legal for an employer to close a company and furlough all his employees at will, even if the company has enough work to sustain its labor pool?

Under our economic system, a company can decide to simply go out of business anytime it wants to, for good reason or for no reason at all.  From what you state in your question, the owner of the business simply decided he or she had enough and closed the business.  That's entirely the owner's decision.  Even though there may have been "enough work to sustain its labor pool," the company may not have been making a profit, the owner may have had personal reasons for closing up, or the owner may have just decided to stop working.  He has a right to make that decision.  The business is not run to "sustain its labor pool;" it is run to make a profit and provide a livelihood for the owners/investors.  The vacation pay may be another matter.  Whether employees are entitled to be paid for "accrued" vacation when a business closed or the employee is terminated often depends on state law, and I don't have enough information here to tell you much.  I suggest you check with the Department of Labor in your state. Finally, I'm assuming the business we're talking about is not large enough to be covered by the Worker Adjustment and Retraining Notification Act, (WARN) so I haven't discussed that in my answer.