Apple has been granted a patent on unlocking a smartphone or tablet using a touchscreen gesture.
The application, which was filed in June 2009, covers a range of commonly used techniques including swiping and pattern entry.
As well as on the iPhone and iPad, such systems are built into Google's Android and Microsoft's Windows Phone 7.
The patent is likely to become another weapon in Apple's arsenal as it continues to sue rival manufacturers.
Devices using the Android operating system have been the focus of particularly aggressive litigation.
Apple co-founder Steve Jobs believed that the product was a rip-off of iOS and vowed to "destroy" it, according to his recently released biography.
To date, his firm has waged a largely proxy war, targeting companies such as Samsung and Motorola which use Google's software.
As a result, Samsung is currently banned from selling its Galaxy Tab 10.1 in Germany and Australia.
Samsung has launched a counter offensive, claiming Apple has infringed technology patents which it holds.
However, on Wednesday, an Italian court turned down Samsung's application for an interim injunction on sales of the iPhone 4S in that country.
Both sides are now expected to submit further evidence.
Apple's patent - US patent number 7657549 - states: "A device with a touch-sensitive display may be unlocked via gestures performed on the touch-sensitive display.
"The device is unlocked if contact with the display corresponds to a predefined gesture for unlocking the device."
The text of the patent is broad and would appear to cover a number of the technologies used by Google and Microsoft in their handheld devices.
However, that did not necessarily mean that Apple would be able to exert its will, according to Silas Brown, an intellectual property solicitor with London-based law firm Briffa.
"Often you will have situations where patents are argued through long and hard to get to registration, but when they are challenged there is a counter action to claim that the patent shouldn't have been granted."
Mr Brown explained that such patents could be invalidated for a number of reasons, including being too broad, too simple or "obvious" in the current technological context.
In Europe, software cannot be patented in its own right. But Apple may still have a case, according to Mr Brown, if the function of unlocking was shown to materially improve the performance of the hardware.
"[Apple's] argument would be more in that direction - that this is an invention which has an effect on hardware, for example security," he said.
Determining that, would likely mean more work for lawyers and specialist engineers.
"The question would go down to a technical analysis and people who are experienced and knowledgeable in respect of this particular type of technology," said Mr Brown.