There is no clear law on what comprises a "substantial" amount of lobbying. In the leading cases upholding IRS decisions to revoke (c)(3) status, the offending charity either engaged in pervasive lobbying, or could not achieve any of its ends except through lobbying. Because it was obvious in all of those instances that the lobbying was more than insubstantial, we have little guidance about how to decide closer cases. Conversely, in the leading case in which a court rejected the IRS’s determination, less than "5% of the time and effort" of the organization was devoted to lobbying. The rules for determining what amounts to "substantial" commercial activity are somewhat more clear-cut. The Tax Court, a federal trial court with jurisdiction to decide tax disputes, has held that a charity whose nonexempt expenditures were about 10% of its total revenues was not engaging in a "substantial" amount of commercial activity. That is, if an organization brings in $100,000, it can spend up to $10,000 on non-charitable activities without losing its exemption. Later cases have emphasized that this 10% figure is not an absolute safe harbor, however. It also is uncertain whether the Supreme Court, which first crafted the "substantial" commercial activity language, would read that term to have the same meaning in the context of lobbying activities.