1. Law/ethics 1
Many assume that ethics simply means obeying the law and professional standards (e.g. Enron case) but…
It can be ethical to break the law, if the law and political situation is very bad e.g. Corporations against Apartheid in South Africa in 1980s. Ogani in Nigeria (case). The philosophy of law, study of law and the common good, is called jurisprudence.
The more ethical people are, the less the need for laws (see virtue ethics)

2. LAW ETHICS Social Acceptability1
LAW
Politics
Jurisprudence
ETHICS
Social
Acceptability
Virtues & Culture

3. A fundamental question in business ethics
Should corporations:
(a) Carefully ensure they obey all the applicable law, or..
(b) Treat the law as a risk factor, comparing the probability and costs of being caught with the benefits of getting away with it. or..
(c) go beyond the law in pursuit of the common good (philanthropy, high environmental standards, employment policies, political engagement, etc.)
(d) lobby politicians to change laws (i) for the common good? (ii) for their own benefit?.

4. One can argue that "obeying the law" just because its the law shows loyalty to the state.  This has some merit but has to be balanced, for example, loyalty to Apartheid SA?, North Korea? Enron?  How far do you go?
By the way, this idea of balance or finding the Mean, in ethics, is usually traced back to Aristotle, the Greek Philosopher around 450BC

5.   Those fish at risk in the Colleton river: we can (i) value them instrumentally (their price, how much we like to eat them, but also their role in the overall ecosystem insofar as it effects people now or in the future). This is called a $ cost benefit approach.  This is also treating the "environment as stakeholder" combined with "instrumental stakeholder theory".  
We can also (ii) value them intrinsically, as "ends in themselves" to use old fashioned language.  This is also "environment as stakeholder" but its coupled to the "normative (Kantian) stakeholder model" (i.e. stakeholder as end in itself).   As you probably know, this is also the "deep green" ethic:. the fish have souls, spiritual value. Maybe the weeds do too...even the stones under some belief systems.  This "deep green" belief seems very ethical and high minded, but it can also be dangerous because it can lead to humans suffering or being harmed to save the fish (or the stone).  So you see everything is a balance.