Following Apple's success in getting Samsung products banned in the EU, Samsung's retaliated by asking a Dutch court to ban Apple's iPads and iPhones too.
In the first hearing into four lawsuits filed by Samsung, the company's claiming that Apple violates its mobile patents.
It says that Apple doesn't have licenses to use 3G technology based on the Universal Mobile Telecommunications Standard (UMTS), despite Samsung's attempts to negotiate an agreement.
Apple says that Samsung's demands were excessive - according to reports, it was demanding 2.4 percent of the chip price on the patents in question.
If Samsung succeeds in persuading the court, it could mean a ban on Dutch sales of the iPhone 5 when it comes out next month.
The decision's likely to hinge on the concept of 'fair, reasonable, and non-discriminatory' (FRAND) terms, under which patents essential to standards conformity are usually licensed.
Apple's arguing that FRAND terms mean that the relevant patents can't be used to block sales of Apple products.
The judge will make a ruling on 14 October.
The companies are now involved in an extraordinary tangle of lawsuits and injunctions. Apple's It's already won a ban on three Galaxy smartphone models in the Netherlands, hitting shipments across Europe.
It's also succeeded in blocking sales of the Galaxy Tab 10.1 in Germany, and has caused delays to its release in Australia.