In answer to your question, no, you cannot acquire copyright protection for a tax loophole strategy. Copyright does not protect ideas, methods, or systems. You may be able to apply for a patent for a tax strategy (the first such patent was issued in 2003), though a recent court decision makes it much more difficult to acquire such patents. In general, the popular sentiment about tax strategy patents is not good and as a senator, President Barack Obama sought to end them.
Finally, you refer to an "unknown tax loophole strategy". By definition, tax loopholes are provisions in the tax code that are exploited for personal gain. Therefore, we assume by using the term "unknown" that you mean you are the first to discover how to exploit an existing tax code provision. That can be dangerous territory (and may sometimes be illegal) and we advise you to tread carefully when touting the benefits of your strategies.