In addition to the issues with Mixed Commission Courts, the Navy's mandate to police the trade was also found to be lacking and built on a series of complicated and often weak diplomatic treaties between other states. The agreements were signed reluctantly and therefore very weak in practice. When policing foreign vessels, there had to be slaves on board at the time of seizure for the accused slaver to be convicted. Unlike in Britain's 1807 act, there was no equipment clause, meaning that slave ships carrying what was obviously equipment for transporting slaves, but without slaves on board at the time of search, could not be seized. This major flaw, which greatly curtailed the Navy's efforts, and caused some naval officers to fall foul of the law, was not rectified until the 1830s. Frustrated with the lack of progress, in 1839 the British government subjected Portuguese vessels to British jurisdiction, and did the same to Brazilian vessels in 1845. This was an unprecedented step which subjected foreign vessels to the much more stringent British law, and much stricter penalties for slave trading.