Import/export laws are some of the most complex ones imaginable.  Every country has a list of tariffs and prohibitions that change on a nearly constant basis.  Failure to follow these procedures can result in huge penalties, and failure to follow proper procedures can also result in large domestic tax liabilities.

For example, this happed in Singapore and became a leading law case there.  A trader in Singaport bought "export only" cigarettes and put them on a ship headed for Japan.  Unfortunately, the shipmaster didn't do the paperwork correctly and the Singapore goverment refused to accept that they had actually left the country, even when the exporter got a statement from the buyer that the cigarettes had reached Japan.  

A good lawyer can keep up to date on upcoming legal changes that might have an impact on an export business.  

Specifically to this example, live plants are subject to numerous restrictions in shipping to prevent the spread of disease and pests.  Importers are not above destroying crops which they fear pose a risk to a domestic market.  Again, these laws can change overnight and a good lawyer can help ameliorate the risk.  

In addition, getting paid is also a problem.  Letters of credit are the usual way to ensure payment, but they too are fraught with technicalities.  For example, a bank can refuse to pay on a letter of credit if they goods are not shipped to a specific address, even if the buyer agreed to the address change.  Again, a good lawyer can help a trading company understand these rules so they don't inadvertently break terms.  Bills of lading (that outline shipping terms) are also subject to misinterpretation.  I have seen cases where loads of goods were ruined in transit and the buyer was stuck with the damaged goods without recourse.