The above examples require all the players realising what is happening. It is a team tactic. This is different to a situation where an individual's knowledge of the rules can benefit his/her team. By coincidence, there is also an example of this from last week. Aaron Smith scores a try by touching the ball against the base of the padded-goalpost (see the YouTube clip here). One must admire the quickness of thought in this action. However, there is a difference of opinion between the commentator and co-commentator. One calls it "clever" while the other calls it "sneaky".
Broadly speaking, economists would not be surprised by the above tactics. A frequently heard mantra is that people react to incentives (the colleague that sent me the link has a blog called Economic Incentives). Many policy recommendations are based on this idea, e.g. increase the tax on a product in order to reduce its consumption. When discussing such recommendations we do not tend to evaluate the motivation on the taxpayer. We just say that they react to incentives.
Things tend to be different when it comes to corporate taxation. Yesterday, the Irish Times carried a story about Kelloggs and corporate tax (here). There is no suggestion of illegal activity. But are companies not just reacting to incentives like the sports people above? Accountants and corporate lawyers are paid vast sums of money to minimise a company's tax bill. For example, they will take advantage of differences between countries tax laws. We are more likely to label such actions as "clever" or "sneaky". However, if there is a problem here then it surely lies with the law makers. Unlike the situation in a sport like rugby, there is not one governing body for tax that can attempt to remedy the situation.